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~~~Charging deep cycle batteries


oldphart

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If you already have one of those small portable battery chargers and want to use it, there is a way to connect it to all three batteries and charge them all at once.

You don’t have to disconnect the batteries from the trolling motor or each other.

Take the charger’s leads and connect it to one of the three. Then with jumper wires of the same gage size or larger of the charger’s cables; connect the other two batteries in parallel. In other words positive to positive negative to negative; like you would while boosting a car’s dead battery.

Even though the batteries are connected in series to get the 36 volts; individually each battery is still only 12V. If you want to confirm this, connect a volt meter to one of the battery’s terminals and then another and you’ll see that they’re still 12 volts.

You can charge fifty batteries this way as long as the charger has the capacity.

The only thing about charging the batteries this way; is that if there is one battery that is partly sulphated (only takes a light surface charge with voltage climbing quickly) the charger (if it’s a voltage sensing charger) will shut down before the other batteries get a full charge.

That’s where a 3 bank charger would be your best bet; it has the ability to sense each battery individually.

Here a crude schematic of what I tried to explain.

 

Dan.

Copy of White picture.jpg

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Charging them independently is best. As for the cranking battery, I know that my Mercury Optimax's computer has a constant draw on the battery, as does the GPS antenna. So, if you park the boat for a long period, i.e. 6-8 weeks you may have a dead battery when you get to the launch. I don't know what make of motor that you have but if has an ECM (i.e computer) then it probably does the same thing. I have a 4 bank DualPro unit on my boat and it does what it's supposed to do.....plug it and forget it. I've had DualPros for 10-12 years, on 3 different boats and they've never failed.

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  • 3 months later...

If you use a 2 bank you'll need to remove the link between the batteries before charging..

 

1 bank is easier for that setup (I had the same in our boat before I switched over to a 24v system)

Thank you Bill, I thought same way.

So basically with 1 bank charger negative is going to 1st battery negative and positive is going to positive on 2nd battery, right?

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  • 2 weeks later...

Guys,

 

I understood how charger needs to be connected. Now please tell me how I should connect trolling motor to those 2 batteries. Is it exactly same way as charger or I can connect it to positive and negative post of first battery and it will do it.

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If you already have one of those small portable battery chargers and want to use it, there is a way to connect it to all three batteries and charge them all at once.

You don’t have to disconnect the batteries from the trolling motor or each other.

Take the charger’s leads and connect it to one of the three. Then with jumper wires of the same gage size or larger of the charger’s cables; connect the other two batteries in parallel. In other words positive to positive negative to negative; like you would while boosting a car’s dead battery.

Even though the batteries are connected in series to get the 36 volts; individually each battery is still only 12V. If you want to confirm this, connect a volt meter to one of the battery’s terminals and then another and you’ll see that they’re still 12 volts.

You can charge fifty batteries this way as long as the charger has the capacity.

The only thing about charging the batteries this way; is that if there is one battery that is partly sulphated (only takes a light surface charge with voltage climbing quickly) the charger (if it’s a voltage sensing charger) will shut down before the other batteries get a full charge.

That’s where a 3 bank charger would be your best bet; it has the ability to sense each battery individually.

Here a crude schematic of what I tried to explain.

 

Dan.

The drawing shows the blue "jumper" going from positive on battery 1 to negative on battery 2 and positive on 2 to negative on battery 3. Is this correct?

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